* add proper INSTALL_POSIX conditional for makefiles
* move all the code to Makefile.am
* rename lyx.desktop to lyx.desptop.in and add proper tags to allow handling of program_suffix.
* add code to install desktop entry and icons under the proper name.
I did not touch scons and cmake, I hope it was not necessary.
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@40531 a592a061-630c-0410-9148-cb99ea01b6c8
